Hello All,
I'm having severe problems with my '93 Dakota, 5.2L (318), Auto, 2wd, Ext. Cab.

Had done a head gasket repair job in Sept. Three weeks after the job, the truck was running great until driving at 75 on interstate, a sudden backfire and engine sags, stalls and then quits. Pull off, can get to fire again, but only barely run, cannot accelerate much past idle. After changing out Distrib cap and rotor, still doing same thing. Changed out Coolant temp sensor since it probed bad, made no difference. After a week of running continuity checks on wiring and static tests on sensors, I took it to a rip off garage. After a charge of $435.00, replaced cam sensor and new plugs, the truck ran great for 20 miles, then started missing...Over a couple days it got worse, running down interstate, starts to sag and then backfire again, cannot go over 20 mph.

Got it home, have replaced PCM, O2 sensor, spark plugs, new wires, cam sensor, rerouted secondary wires per TSB, distrib cap and rotor. Had new battery put in to replace a 2 month new battery though the battery shop tech said the one I had was fine. Replaced with OEM spec battery, before replacement, I could not start, after new OEM battery, it started ok..still sags when running down over idle. Backfiring when let up on accel. Runs great when cold, once it warms up, goes into closed loop, starts running same way, backfiring, like not advancing as should. I've reindexed the distib per TSB spec. Throwng code 25 and 62 now. This is fisrt it has thrown codes since problem started. It's a refurbished PCM. Code 62 says it cannot write to eeprom. The replacement PCM was same number as on vehicle. I was told they were pre-programmed.

I've determined it is happening when it warms to operating temp. The PCM coolant temp sensor was replaced also. Lookng at wire scematic, the PCM ignition/emmisions circuit has a distance sensor in the circuit, common ground with O2, MAP, Crank, Cam, Intake Temp sensors.

All the techs tell me they can't do much to see what the engine is doing because of year (1993) and scan or diagnostic tools will not work.

I would sure appfreciate any suggestions or ideas. I don't like throwing new parts on, too much money and I'm disabled with limited budget. Already spent close to $1K now with the repairs and parts.

Thanks for reading,

Whit

 

ive seen similar things happen with a bad Catalytic Converter on a jeep, might be part of the problem

 

You have not said anything about the coil,did you test ? Get one and try it, there not that expensive and you'll have a spare. And I assume you must have the check engine light on.


You can cycle the key on,off,on,off,on ,and the CEL will blink. Pair the numbers up between the pauses and post the results here, and some one will help you with the codes.

 

As he said in his earlier post:
"Throwng code 25 and 62 now. This is fisrt it has thrown codes since problem started. It's a refurbished PCM. Code 62 says it cannot write to eeprom. The replacement PCM was same number as on vehicle. I was told they were pre-programmed."

Code 25 means target idle not reached, or there is an issue with the idle air control valve.
Code 62 means SRI mile not stored.

Like fishlessman said, minus the stored trouble codes, sounds like it could be a bad catalytic convertor (when they go bad, they can make the truck run really weak, basically having no power).

 

you sir have just described to the detail the same problem i am having. luckily its usually ok enough to get to school and back, but just today I got it to school... just not home. For what ever reason i can go 25 instead of 15 with over 1/4 tank o gas on a bad day, so that got it home... regardless...

I personally pulled the cat (and dropped a glasspack in its place...) and that did nothing to solve the problem. That doesn't mean you could still try it, but the similarities are so close its not even funny...

I haven't gotten around to re indexing the distributor... but I also suspect it could be a bad timing chain, and did notice recently that my coil is making quite a bit of noise (almost a clicking sound, as if its arcing, only i can't see it)

for w/e reason ive been throwing a code 15 (speed sensor) and for the life of me I can't figure out why. theoretically it shouldn't have an effect on any of this, but its the only code i got ( and occurred after this all started... ive managed to get around the area with it like this for the last 6 months or so... starting to get sick of it because I can't take the freeway)

 

Sorry, I read it and took it as he was talking about the original PCM.

 

FRom my investigation, your code 15 (speed sensor) could be referencing the "distance sensor". Per my 1992-93 wiring schematic, the distance sensor is on the same circuit as all the other timing/F.I. sync circuit.

My rig has a pigtail coming out of the sensor, same place the cable exits. The BLK/L-BLU wire indicates it is on same circuit. My book has no reference to the distance sensor other than in the wiring schem. Have no idea what a static reading should be.

From all the negative responses of techs, there seems to be no way to connect a computer up to the PCM on this rig, being it a pre-1996 - OBD-II. But, being a computer tech, if it's got logic circuits, there has to be a way to connect up to the serial line to grab the data. I've just had no luck in finding enough info to make up a connector cable to input to my laptop. It would sure be nice to see what the PCM is doing when it's trying to run.

Good luck to you and thanks for your response.

Whit

 

I have done static tests on the coil after seeing such a weak spark off plugs. It checked out fine to spec however. One interesting thing was the battery. I think I posted about the new battery and the new "OEM" spec battery starts this thing in this whatever mode when the other less CCA battery could/would not start it. The battery tech was reluctant to change out the old battery but when he said lets test the OEM bat. and it worked first attempt, he was willing to exchange with a little added $ to cover the price difference.

I pulled apart, cleaned and applied dielectric grease to all connectors yesterday with some improvement. I still have the intermittent but always there inability to go above certain RPM without it bogging down seriously that it backfires. With the code 25 now, the idle is bad, stalls and hard to drive. I probed for shorts in the IAC motor but find none. With the code, I suspect the PCM may be at fault.

This has been a 6 week headache now. Lots of $$ and still not running. Nice thing is gas is down to $1.55 per gal. I'd like to take advantage of the low price! Fill up for $30.00 is something havent seen for quite a while!

Thanks for you help!!

Whit